ASCA observations of type-2 Seyfert galaxies: II. The Importance of X-ray Scattering and Reflection

We discuss the importance of X-ray scattering and Compton reflection in type-2 Seyfert galaxies, based upon the analysis of ASCA observations of 25 such sources. Consideration of the iron Kalpha, [O III] line and X-ray variability suggest that NGC 1068, NGC 4945, NGC 2992, Mrk 3, Mrk 463E and Mrk 273 are dominated by reprocessed X-rays. We examine the properties of these sources in more detail. We find that the iron Kalpha complex contains significant contributions from neutral and high-ionization species of iron. Compton reflection, hot gas and starburst emission all appear to make significant contributions to the observed X-ray spectra. Mrk 3 is the only source in this subsample which does not have a significant starburst contamination. The ASCA spectrum below 3 keV is dominated by hot scattering gas with U_X ~ 5, N_H ~ 4 x 10^23 cm^-2. This material is more highly ionized than the zone of material comprising the warm absorber seen in Seyfert~1 galaxies, but may contain a contribution from shock-heated gas associated with the jet. Estimates of the X-ray scattering fraction cover 0.25 - 5%. The spectrum above 3 keV appears to be dominated by a Compton reflection component although there is evidence that the primary continuum component becomes visible close to 10 keV.Comment: 27 pages, 6 figures. LaTeX with encapsulated postscript. To appear in the Astrophysical Journal. Also available via http://lheawww.gsfc.nasa.gov/~george/papers/gnt_s2p2/abstract.htm

The genomic basis of cichlid fish adaptation within the deepwater “twilight zone” of Lake Malawi

Deepwater environments are characterized by low levels of available light at narrow spectra, great hydrostatic pressure, and low levels of dissolved oxygen—conditions predicted to exert highly specific selection pressures. In Lake Malawi over 800 cichlid species have evolved, and this adaptive radiation extends into the “twilight zone” below 50 m. We use population-level RAD-seq data to investigate whether four endemic deepwater species (Diplotaxodon spp.) have experienced divergent selection within this environment. We identify candidate genes including regulators of photoreceptor function, photopigments, lens morphology, and haemoglobin, many not previously implicated in cichlid adaptive radiations. Colocalization of functionally linked genes suggests coadapted “supergene” complexes. Comparisons of Diplotaxodon to the broader Lake Malawi radiation using genome resequencing data revealed functional substitutions and signatures of positive selection in candidate genes. Our data provide unique insights into genomic adaptation within deepwater habitats, and suggest genome-level specialization for life at depth as an important process in cichlid radiation

Elemental Abundances in NGC 3516

We present RGS data from an XMM-Newton observation of the Seyfert 1 galaxy NGC 3516, taken while the continuum source was in an extreme low state. The spectrum shows numerous emission lines including the H-like lines of C, N and O and the He-like lines of N, O and Ne. These data show that the N lines are far stronger than would be expected from gas of solar abundances. Based on our photoionization models, we find that N is overabundant compared to C, O and Ne by at least a factor of 2.5. We suggest this is the result of secondary production of N in intermediate mass stars, and indicative of the history of star formation in NGC 3516.Comment: 19 pages, 3 color figures. ApJ in pres

Statistical Algorithms for Ontology-based Annotation of Scientific Literature

Background: Ontologies encode relationships within a domain in robust data structures that can be used to annotate data objects, including scientific papers, in ways that ease tasks such as search and meta-analysis. However, the annotation process requires significant time and effort when performed by humans. Text mining algorithms can facilitate this process, but they render an analysis mainly based upon keyword, synonym and semantic matching. They do not leverage information embedded in an ontology’s structure. Methods: We present a probabilistic framework that facilitates the automatic annotation of literature by indirectly modeling the restrictions among the different classes in the ontology. Our research focuses on annotating human functional neuroimaging literature within the Cognitive Paradigm Ontology (CogPO). We use an approach that combines the stochastic simplicity of naïve Bayes with the formal transparency of decision trees. Our data structure is easily modifiable to reflect changing domain knowledge. Results: We compare our results across naïve Bayes, Bayesian Decision Trees, and Constrained Decision Tree classifiers that keep a human expert in the loop, in terms of the quality measure of the F1-mirco score. Conclusions: Unlike traditional text mining algorithms, our framework can model the knowledge encoded by the dependencies in an ontology, albeit indirectly. We successfully exploit the fact that CogPO has explicitly stated restrictions, and implicit dependencies in the form of patterns in the expert curated annotations

The X-ray Emission from the Nucleus of the Dwarf Elliptical Galaxy NGC 3226

We present the first high resolution X-ray image of the dwarf elliptical galaxy NGC 3226. The data were obtained during an observation of the nearby Seyfert Galaxy NGC 3227 using the Chandra X-ray Observatory. We detect a point X-ray source spatially consistent with the optical nucleus of NGC 3226 and a recently-detected, compact, flat-spectrum, radio source. The X-ray spectrum can be measured up to ~10 keV and is consistent with a power law with a photon index 1.7 <~ Gamma <~ 2.2, or thermal bremmstrahlung emission with 4 <~ kT <~ 10 keV. In both cases the luminosity in the 2--10 keV band ~10^{40} h_{75}^{-1} erg/s. We find marginal evidence that the nucleus varies within the observation. These characteristics support evidence from other wavebands that NGC 3226 harbors a low-luminosity, active nucleus. We also comment on two previously-unknown, fainter X-ray sources <~ 15 arcsec from the nucleus of NGC 3226. Their proximity to the nucleus (with projected distances <~ 1.3/h_{75} kpc) suggests both are within NGC 3226, and thus have luminosities (~few x 10^{38} -- few x 10^{39} erg/s) consistent with black-hole binary systems.Comment: Accepted for publication in ApJ. Figures in colo

Wildlife Harvesting and Sustainable Regional Native Economy in the Hudson and James Bay Lowland, Ontario

To assist the Omushkego Cree in planning a community and regional economic development strategy that takes into account the traditional economy, we developed appropriate methodologies to investigate the quantitative importance and economic value of hunting and fishing for the Mushkegowuk region, Hudson and James Bay Lowland. Harvests of wildlife by the 6500 aboriginal residents of eight communities - Moose Factory, Moosonee, New Post, Fort Albany, Kashechewan, Attawapiskat, Peawanuck and Fort Severn - were estimated by means of a questionnaire study. A total of 925 persons were interviewed for 56% coverage in a stratified sampling design. Four species (moose, Canada goose, caribou, lesser snow goose) accounted for about two-thirds of the 1990 bush food harvest of 687 000 kg, the equivalent of 402 g meat or 97 g protein per adult per day. The replacement value of the bush food harvested in the region was about $7.8 million in 1990. Including other products of the land (fur, fuelwood, berries), the total value of the traditional economy,$9.4 million for the region or $8400 per household per year, was about one-third as large as the total cash economy. The results show that the traditional economy is a cornerstone of the regional mixed economy, and that such a mixed economy may persist as a culturally and environmentally sustainable base for the region.Key words: Hudson Bay and James Bay Lowland, Canadian subarctic, Cree, sustainable development, subsistence, wildlife, fisheriesDans le but d'aider les Cris Omushkego &agrave; planifier une strat&eacute;gie de d&eacute;veloppement &eacute;conomique communautaire et r&eacute;gional qui tienne compte de l'&eacute;conomie traditionnelle, on a mis au point des m&eacute;thodologies appropri&eacute;es permettant d'enqu&ecirc;ter sur l'importance quantitative et sur la valeur &eacute;conomique de la chasse et de la p&ecirc;che pour la r&eacute;gion de Mushkegowuk, dans les basses-terres de la baie d'Hudson et de la baie James. Une &eacute;tude faite &agrave; l'aide d'un sondage a permis d'&eacute;valuer le nombre de prises d'animaux par les 6500 autochtones habitant les huit communaut&eacute;s de Moose Factory, Moosonee, New Post, Fort Albany, Kashechewan, Attawapiskat, Peawanuck et Fort Severn. Un total de 925 personnes ont &eacute;t&eacute; interview&eacute;es formant 56 p. cent d'un plan d'&eacute;chantillonnage stratifi&eacute;. Quatre esp&egrave;ces (l'orignal, la bernache du Canada, le caribou et la petite oie blanche) comptaient pour environ les deux tiers des prises provenant de la nature au cours de l'ann&eacute;e 90. Le poids de ces prises &eacute;tait de 687 000 kg, soit l'&eacute;quivalent quotidien de 402 g de viande ou de 97 g de prot&eacute;ine par adulte. La valeur de remplacement de la nourriture tir&eacute;e de la nature dans la r&eacute;gion &eacute;tait d'environ 7,8 millions de dollars en 1990. Si l'on inclut les autres produits de la nature (fourrure, bois de feu, baies), la valeur totale de l'&eacute;conomie traditionnelle - 9,4 millions de dollars pour la r&eacute;gion ou 8400 dollars annuels par foyer - &eacute;quivalait &agrave; environ un tiers de l'&eacute;conomie mon&eacute;taire totale. Les r&eacute;sultats montrent que l'&eacute;conomie traditionnelle est un pilier de l'&eacute;conomie mixte r&eacute;gionale et que cette derni&egrave;re peut persister en tant qu'assise durable sur le plan culturel et environnemental pour la r&eacute;gion.Mots cl&eacute;s: basses-terres de la baie d&rsquo;Hudson et de la baie James, subarctique canadien, Cris, d&eacute;veloppement durable, subsistance, faune, p&ecirc;cherie